The keyboard is also of the highest quality. The keyboard's chassis is actually brush aluminum. Real metal. (you can crack a skull with it) The keyboard's cable is nothing you've ever seen. It's very thick, wrapped with some type of cloth-like material, kinda like high-class electric cable you find in antic stores.

Corsair keyboard braided cable.

It seems to require 2 USB ports. However, the keyboard also has a USB port (pass-thru, not hub). According to their tech support post on amazon, the second USB is for the purpose of the pass-thru port.

The back of the keyboard, showing the USB port, and the Windows Lock key (it prevents the ❖ Win key from activation.).

The 20 Key Roll-over (20KRO) on USB is quite interesting. A normal PC keyboard has problem registering certain combination of 3 or more keys held down simultaneously.
Majority of USB-based gaming keyboard, has special circuitry so that they can register 6 keys simultaneously. But 6 is the typical maximum, due to USB protocol. Here, they took care of this issue, and allows 20 key key-rollover over USB.
〔➤ Keyboard Ghosting; How Many Keys Your Keyboard Can Take?〕

K90 requires software, for those extra function keys. The K60 doesn't. I'd recommend the K60, because people on amazon have reported problems with the software and the key lighting. The extra G keys also makes the keyboard extra wide. For extra function keys, you can use AutoHotkey to program the number pad keys. 〔➤ AutoHotkey Tutorial ⌨〕